Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 07 2013, 03:13AM

Images

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Mon Jan 07 2013, 03:18AM

I would most definitely be very interested.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Nik, Mon Jan 07 2013, 04:03AM

Very cool looking bit of kit, right down to the cuts to stop creepage. What is the intended input voltage for the CW multiplier? I can guess but I am but a lowly electrician, bannished from the land of engineering ;) I'm in Canada so I'm not looking for a sample, just curious.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Mon Jan 07 2013, 07:39AM

Hi Allison, My name is Harrison and I am very interested in trying this out! I think it is so cool that EVR gives the community an opportunity like this to help out and evaluate a product! Id be more than happy to test one out and provide you with feedback to better help your production of the product and other future products that may stem from this

Re: Marx Generator Kits - FREE Kits for Evaluation!
Shrad, Mon Jan 07 2013, 10:19AM

interested in testing this on a N2 laser cartridge (marx or CW with triggered spark gap)

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Jan 07 2013, 03:32PM

Dam, too bad I'm in the UK as I would have loved to have evaluated one of these kits.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 07 2013, 03:40PM

We can ship internationally if you do pay the shipping which will be about $20.00.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Jan 07 2013, 04:16PM


Thanks.

I am interested and have sent you a PM.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Erlend^SE, Mon Jan 07 2013, 04:56PM

What would it cost to buy the kit + shipping to Norway/EU?

Any recommended power-supply?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Sulaiman, Mon Jan 07 2013, 06:42PM

Just an obvious warning .....
assuming that the multiplier is fed from ac line;

USA 110/120 Vac is half of UK (240Vac), Europe (220Vac) etc.
so the multiplier capacitors and diodes should be >= 800 V pk rated
and the Marx Generator dc input will be twice expected
unless the number of multiplier stages is reduced/halved.

You could either make two pcb versions using higher voltage rated devices
OR re-do the pcb to allow
2x(>=400V) diodes in series and 2x (>=350V) capacitors in series as an option.

Less critical is the line frequency, giving better output on 60 Hz then 50 Hz


I like the spark gap holes.
A good area for experimentation is the spark gaps;
material/pointiness/optical alignment etc.
maybe a project for receivers of the sample kit ?

Unfortunately my 'scope probe only goes to 40kV
and I haven't a present need for a Marx generator or I'd volunteer.

Also, a small warning ...
warn users of potential x-ray and/or u.v. hazard as well as noise/fire/electric shock/etc.

ALSO: you should consider some on-pcb resistance at the multiplier output
as well as the Mark generator input
because I made a 15-stage (30x 1N4007 & 10n 1kV cer.) multiplier from an ionizer kit
and blew it up by bypassing the on-board series output resistors !

Re: Marx Generator Kits - FREE Kits for Evaluation!
Weston, Mon Jan 07 2013, 07:23PM

I would be interested in testing one of the kits. I have experience assembling such kits and the proper knowledge of electrical safety.

I have the test equipment to measure the output voltage of the CW and the current output of the marx too. Sounds like something fun to try.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Ben Solon, Mon Jan 07 2013, 10:13PM

Very cool! they might work well for dielectric analysis as well on a small scale. I like how they're mounted right on the pcb, I hope they don't start breaking down. If any are still available, I live in Massachusetts and would definitely like to beta test one.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Meatball, Tue Jan 08 2013, 12:50AM

I've got the time and tools to put something together and evaluate it. I'm in NE, let me know if there are any more samples to test.

Re: Marx Generator Kits - FREE Kits for Evaluation!
E.TexasTesla, Tue Jan 08 2013, 02:44AM

Looks nice. Maybe someone could post a video of it in operation. I bet its noisy.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Polonium210, Tue Jan 08 2013, 05:36AM


I as well am interested. PM sent.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Wed Jan 09 2013, 10:54AM

I'm in WI and I would be interested in testing one of these kits if any are still available. Very professional looking boards. Great work!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Myke, Wed Jan 09 2013, 11:17AM

If there are any more still available, I'd be interested in testing one out.
-Khalil Elbaggari

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Wed Jan 09 2013, 01:51PM

Thank you everyone for the interest in these kits. I will be contacting you via PM to get your addresses so i can ship out the kits to you. Thanks again!

Re: Marx Generator Kits - FREE Kits for Evaluation!
rp181, Wed Jan 09 2013, 07:52PM

If you still need more people, I would love to try one out.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Chip Fixes, Thu Jan 10 2013, 04:45PM

Same with rp181, I also have the equipment to measure various aspects of the CW.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Fri Jan 11 2013, 12:56AM

Thanks for all the responses. I'm so excited. Waiting on some parts, but will start contacting you all in the next few days. Thanks again guys!

Allison

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 14 2013, 02:42PM

UPDATE:

PM's sent to the first responders here. Unfortunately, we only have a limited amount of kits, so we weren't able to accomodate everyone. Sorry.

Please following instructions on PM with your name and address information.

These are free kits and all I ask in return is your comments and feedback and well as how well your kit performed. If you loved 'em, if you hated 'em. If you think they're great - if you think they stink. All feedback appreciated!

Also, as Suilaman pointed out, if you are international, you may need to use alternative capacitors on the CW multiplier and/or use a different input source. The input source is rated for 120VAC operation. The capacitors on the Marx. are rated for 6kV.

Thanks for you interest.

Allison

Re: Marx Generator Kits - FREE Kits for Evaluation!
Marko, Mon Jan 14 2013, 04:37PM

Hi Allison

May I offer some evaluation/advice without you having to send a kit to me? :)

The spark gaps in your marx seem to be made simply from bent capacitor pins. While I can see this was the easiest solution here, I wouldn't recommend it for several reasons:

- The thin wires could be easily bent by handling or transport, and setting them back to their original position can be painstaking.

- Even worse, they could quickly suffer metal fatigue and get torn completely.

- The sharp edges of the wires render the gaps even more difficult to adjust, because breakdown voltage will wary greatly depending on how the wire was cut. That's why people bend the wire ends into little loops on their marx generators!

Ideally, you want all the gaps to fire reliably at almost the same voltage, which is just a bit less than your maximum charging voltage for the best effect. There are a number of ways to construct good spark gaps, but here's one idea that just fell to my mind:

Buy a bag of small decorative acorn/dome brass nuts like these:

Then solder them from beneath the PCB, facing each other. Before soldering, space them with an adequate spacer (which could be a sheet of thick paper or a thin PCB). I've had good success with simple spark gaps made this way.

Marko

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 14 2013, 05:51PM

Thanks Marko. Thats an excellent tip. I had thought about using a different type of electrode configuration, but most of my ideas were too cost prohibitive. The acorn nuts look like a great idea. If they can be easily soldered by the typical general purpose soldering iron to a pad then that would be a great solution. A suitable spacer could then be included in the kit for the proper distance.

Thank you Marko

Allison

Re: Marx Generator Kits - FREE Kits for Evaluation!
Marko, Mon Jan 14 2013, 07:14PM


Hi Allison

To facilitate soldering of the brass nuts, it is a good idea to sand the surfaces that are going to be soldered with some fine grit sandpaper. Small M3 or similar sized nuts shouldn't be a problem to heat up and solder with any hobbyst soldering iron.

If you're lucky, you might even be able to get some nickel plated brass nuts (rare in my country) which should be even easier to solder as they resist oxidation.

Marko

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Tue Jan 15 2013, 07:03PM


Thanks, just replied to it and payed for shipping to the UK.

I look forward to testing this kit out and being a beta tester!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Inducktion, Tue Jan 15 2013, 08:33PM

I've also seen some people use ball bearings as the sparkgaps. How you would solder them though is another thing...

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 21 2013, 07:12PM

These have all shipped! Thanks again!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Fri Jan 25 2013, 04:47AM

Mine arrived today and it looks very cool. I have started building it but it appears R1 and R2 of high voltage multiplier 1.0 are missing.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Fri Jan 25 2013, 05:17AM

I noticed that too.
Here's a short video of everything that's included in the kit as well as some comments on the assembly

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Fri Jan 25 2013, 09:45PM

Mine arrived today! I'm excited to put it all together and as the others have said my kit is missing the 2 30k reistors as well. What value resistors will work as a replacement since i'm currently out of 30k's and also the required wattage. I'm just unsure of the minimum requirements. Thanks.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Sat Jan 26 2013, 07:39PM

I think the purpose of R1 and R2 are generally for safety. If you look at most CW multipliers, there are no resistors unless you need it for a specific power input and/or just for safety reasons.. (I think). For those of us in the US using 110-120vac, this shouldn't be a problem as long as the current isn't real high and R1 & R2 can probably be bypassed with a piece of wire. However I would not yet go that route until we hear from EVR. For those in the UK, will need to step down their voltage and use resistors probably

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Sun Jan 27 2013, 03:04AM


+1 for the heads up on soldering the diodes in place first. It seems obvious now you have mentioned it but this is exactly the sort of thing I normally find out when its too late.

Still waiting for my kit to arrive on this side of the Atlantic, and I hope customs don't decide to put up a fuss

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Jan 28 2013, 01:35AM

Yes, just use jumper wires for those two resistors.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Mon Jan 28 2013, 04:27AM

This might be a stupid questing but how do you put the capacitor legs? i cant seem to get it to do anything and i have tryed several configurations.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Mon Jan 28 2013, 04:51AM

Not exactly sure what you mean. They don't have polarity and doesnt matter which way they are oriented, or are you unsure how they are to be installed? Show us a pic of what you are doing if possible

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Jan 28 2013, 06:40AM


Are you talking about using the capacitor legs on the marx board as spark gaps?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Mon Jan 28 2013, 08:17AM

I dont really know anything about how to determine spark gap lengths. I've read something before about it but dont really remember... Trial and error seems best. For this kit I would guess anywhere between 2-5mm is a good place to start. What do you guys think?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Mon Jan 28 2013, 10:50AM

like what leg connects to what leg i tryed straight across and i could get them to all fire but no output and i tryed in a Z configuration and could not get them to fire. And i got not output with ither. Also return is just connected to input - right?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Jan 28 2013, 01:46PM

Just letting easternvoltageresearch/Allison/Dan know that my kit has arrived safely here in the UK.

I must say I really do like the black PCB design, its really nice! feels really sturdy too so vertical mounting is a practical choice.

So far I have soldered all of the components in place and have configured the spark gaps, I just used the leads of the capacitors for the electrodes. I haven't powered it up yet but will do the initial low power tests tomorrow after college (the local ham radio guy is going to hate this one!).




This is how I currently have the spark gaps set up. Will probably need some tweaking though. I good tip here is to leave some space between the capacitors and the board, this gives you some headroom to adjust the spark gaps with out having to use some needle nose pliers like I am



Tomorrow I will have a real play with it and will be able to give some real feedback.

(Mods let me know if these images are too big and I will change them to smaller ones).

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Mon Jan 28 2013, 03:19PM

Z configuration. Not straight across, thats bad. You want to keep them configured in parallel, so that when the energy becomes great enough the spark gaps fire to connect in series. Try the opposite Z configuration that. you already did. If you look closely at the pics posted by Allison, you can sort of tell. I'll be posting another video of operation when get mine fired up ( if I get it to fire up ) and I'll point this out.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Tue Jan 29 2013, 01:23AM

Alex, I like how you placed the spark gaps right in the center of the holes, good for visual reference.

Here are some pics of my almost ready setup.








Mounted it on a scrap piece of PCB. I've done tests already, currently uploading a video and will edit it in when its done. Now I am going to go see how I can make it better! :)

Edit, Here's the video a little overview and operation
I cant seem to get it to fire anymore, It really just sparks when it wants to... I'm wondering if the Rb is a little to high for this? It might just take more tweaking around.

-Harry

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Tue Jan 29 2013, 02:48AM

Looks great guys! We actually haven't finished testing our own boards. We had benchtop tests that worked great, but they used different capacitors. We plan to get around to building these up real soon - just had another pressing issue we had to work on first.

But everything looks great. Excited to see how you guys make out with them. And if there is a problem, hopefully we can get it pointed out. Hopefully there isn't a mistake in the board artwork.

Thanks again!

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Tue Jan 29 2013, 05:15AM

Just tried to power mine up however i am having some issues. First thing i did was check the voltage on the multiplier it wasn't getting to high so i checked all the caps and diodes and noticed i was missing a trace between cap 12 and 14 jumpered that one together thinking AHA found the problem. Well to my suprise i'm still not getting anything at all out of the marx and i have my gaps set very very close. I'm not sure what the issue is and i am certain i have the marx configured correctly. I believe my issue is something with the multiplier board. Anyone else having issues? I will try and figure it out more in the next few days and also get my camera back to snap some photos.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Tue Jan 29 2013, 11:21AM

I think im having the same problem. Like the output it just puting out a tiny tiny spark that dosent look like its over 1mm?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Tue Jan 29 2013, 01:02PM

My hypothesis is that the marx gen caps arn't charging properly, and performance is at its minimum with the spark gaps. I've experienced a bit of premature firing I think, however when I increase SG distance over 1.5mm It doesn't fire. How do you guys have your spark gaps configured? And how are you powering the whole thing?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Tue Jan 29 2013, 07:24PM

@Physics Junkie what value are the resistors on your marx board? as in the video you uploaded they look like 10 ohm resistors.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Tue Jan 29 2013, 08:29PM

My gaps are configured just like in your video Physics Junkie. I have spaced them all with a thin piece of plastic and made sure the first gap is a little closer than the rest. My output from the marx is only gapped about a 1/4 inch. i'm gonna split the boards up later and see what kind of output i can get off the multiplier itself. As i said earlier i was missing a trace between cap 12 and 14 so its possible i may have missed seeing another error on the pcb. Also i am powering it straight off my variac and have cranked it up to around 130 volts AC measured by my multimeter. I think i should have gotten atleast something to spark with my gaps on the marx set so close together but nadda. I'll keep you guys updated.


Edit: I've tested the voltage multiplier by itself with a lower volatge AC transformer. 18 Volts input after 5th stage i hit 101ish volts after that it starts dropping and i get no more than 70 volts out at the end of the multiplier. At 18 volts in i think i should be seeing about 430 volts so its definetly something screwy in the multiplier. Now to find out which component is faulty as i have checked them all on board and all seem fine. Time to start desoldering i guess!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Tue Jan 29 2013, 10:49PM

1M ohm I think maybe 2M. Ill double check this and let you know. I sure hope they are not 10 ohm lol

EDIT: 1M ohm, gold green black brown rings.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Electra, Wed Jan 30 2013, 02:07AM

HB, To be fair 18v may be to low an input voltage for a reliable test, if the voltage difference between each stage and the next, is that of across the preceding stage’s capacitor less the voltage drops of the diodes. As you go up the ladder due to the high number of stages the percentage loss out of a lower voltage becomes larger. At 100’s volts per stage it becomes almost insignificant

The current also gets less the more stages there are, so any loading has a greater effect. If this is a problem this can be offset somewhat by using increasing higher value capacitances for the stages as they get nearer the bottom.

Eastern volts research has done a nice job of the boards, and I’m sure has worked everything out correctly. Diodes can fail in peculiar ways and pass some current rather than go completely open or short circuit, which can not be obvious to detect at first.

If it wasn’t for me being in the UK makes me wish I’d requested one, but appreciate the hassle and cost with the postage.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Wed Jan 30 2013, 03:56AM

So far the only things I would suggest be made differently are:

1) Thicker Traces, You can sort of see the traces under the solder mask. My opinion is that they are quite thin for high voltages.
2) Higher capacitance for each cap on the multiplier, as Electra pointed out.. thank you.
3) Some sort of solder pad or mount for utilization of improved spark gaps.
4) Xenon or Neon light indicator at the input on the Marx generator. I've seen some other marx generators that use the straight xenon tubes and it flashes when the caps are fully charged/first spark gap fires. It would also be a good way to indicate whether or not the caps are charging.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Wed Jan 30 2013, 04:57AM

Don't get me wrong i know EVR does good work. I don't think its the boards. I was first running this from my variac and i couldn't even get a spark to jump from just the multiplier at 125 AC input. My thought is that i have a bad diode somewhere and i have gotten a random bad part before even when new. So in no way am i blaming EVR as others have gotten it working.

As for the trace missing it was an easy fix and i doubt it was anyones fault things just happen and can't always be perfect. I agree with you Electra about the diodes my guess is one of them is bad and thanks for the input on the testing i just found it odd that it goes up just fine for the first 5 stages and then declines and stays same voltage for the rest of the stages.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Wed Jan 30 2013, 05:24AM

I too just discovered no trace between cap 14 and 16 on mine.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Wed Jan 30 2013, 01:21PM

Aha! Great works guys! Missing trace. That would explain why my board here isn't working either! Well, thats why there is beta testing! Appreciate the work and effort. You'll all get new boards / kits when I do the revisions after these are testing.

I should be able to build mine up today.

Thanks again!

Allison

Re: Marx Generator Kits - FREE Kits for Evaluation!
Shrad, Wed Jan 30 2013, 01:35PM

cant wait to get it in the mailbox!

I hope it will be nice for the TE nitrogen laser cartridge I want to run

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Wed Jan 30 2013, 07:16PM

Glad to be of service EVR I'd be happy to test for you anytime!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Wed Jan 30 2013, 07:49PM

Well, I thought so too. But there is still some sort of problem with the marx caps not charging fully. When I bring the output spark gaps a few mm apart I get corona and the caps get drained, which is no good. They are charging but it seems not enough to fire. This could be because of the following:
1) need more capacitance
2) may also be a missing trace on the marx board
3) Rb may need to be different value.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Thu Jan 31 2013, 12:26AM

I wonder if its the capacitors. These are new caps that were selected - different from the ones i used on the prototype. I will upload datasheet.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Thu Jan 31 2013, 12:48AM

My kit is working great, will post some video footage and photos when I get back.

I will say this though, the spark gaps are VERY sensitive and need to be just right to fire at the same time.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Thu Jan 31 2013, 01:39AM

Good to hear!

I figured the spark gaps were gonna be tricky.. what distance would you say they are? I'll have to mess around with mine a bit more

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Thu Jan 31 2013, 02:33AM

Second attempt at typing this out, I got a bluescreen last time (think I might have a bad stick of RAM).

Anyway, yes the spark gaps played a big part in getting it to work. That faint noise when there is no output for me turned out to be one of the spark gaps firing prematurely and discharging all of the other caps. Look at the spark gaps really closely and see if one of them has a small arc across it.

@Physics Junkie My gaps are around 1.5mm's each, with both electrodes pointing at each other rather than vertical like a jacobs ladder which is what I originally had them like.

I think having them pointed at each other is normally avoided with some of the bigger/higher input voltage marx's, but at lower voltages they seem to help "encourage" the gaps to fire.





I ran into a slight problem with R2 going open circuit after a few test fires. Not sure if that is becuase its too low wattage or if I simply got a dud, but it is in the path of the HV return for the marx. After replacing it with a higher wattage one and by-passing it from the HV return it has been fine.

By bypassing it I mean using an external resistor or no resistor at all (haven't had any problems so far in doing that).





Video of it running, I'm only putting around 2kV in so the final output is not at its greatest potential (pun intended).



I should note that I am not using the HV multiplier board since I live in 240v land and have no variac. The Marx is connected directly to a small inverter that gives around 1.5-2kv, can't be sure for certain though since I have no "official" way to measure it.

I have also bypassed the 4.7Mohm resistor for the time being with a smaller one since I am using a lower charging voltage.

Also checked the multiplier board and found C16 to indeed be isolated from the diodes and C14, so its defiantly a mistake in manufacturing.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Thu Jan 31 2013, 05:51AM

Very nice Alex! I did notice several premature fires though. You might be able to get away with a more distance on the gaps perhaps?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Polonium210, Thu Jan 31 2013, 07:09AM

I got mine in the mail today. It is a very nice looking kit.

After correcting the missing trace between C14 and C16 I got a few sparks before it quit.
I had the lights off and noticed some corona coming from R2 on the Marx board. R2 failed open.
I jumpered R2 out, now I only get a 1/2 inch spark about every 5 seconds.

Is the consensus on the spark gaps to face the pointed ends of the cap leads together?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Thu Jan 31 2013, 07:51AM

So it seems. Of course point them in series though..

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Thu Jan 31 2013, 05:56PM


Thanks. I did play around with the spark gaps quite a bit and have come to the conclusion that my charging voltage is just too low for any larger spark gaps. If one of them was too large then non of them would fire, or the one with the smallest gap would fire and a continuous arc would form.

Edit: I think it might just be the effect of the camera's rolling shutter (CMOS sensor), sparks taking place between frames etc.

I am going to make a regulated power supply for this at some point, since the capacitors are rated at 6kV each I am thinking of aiming for the 4.5-5kV mark to leave for some headroom. I was thinking of using a UC384x + feedback loop of some sort to shut the supply down on short circuit or over voltage.


I had the exact same thing on mine, R2 went open circuit after a few runs and I recall there being some arcing around that area before it failed. What I suggest is replacing it with another 1Mohm resistor and then soldering a wire directly to the capacitor leg after R2 for your HV return, bypassing the resistor from the HV return path.

If you wanted to then limit the discharge current use a much smaller higher wattage resistor of about a few 10k, any higher than this and the discharge arc is too faint to see in a moderately lit room (if arcs are your primary goal, for other applications it might be fine).

Also try bypassing the large charging resistor with a much smaller one, the 4.7Mohm is overkill and really slows down the burst rate. I put a 150k in parallel with the charging resistor on mine, this was for 1.5-2kV charging voltage so you might want to use something like 200-300k for the multiplier board.

BTW How much current does the whole set-up draw when the multiplier board is used? I just did some calculations and @ 60hz the capacitive reactance of a 100nF capacitor is 26.526 Kilohms.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Fri Feb 01 2013, 01:57AM

Excellent, thanks for posting the video. I'm so glad you got such great results. Spark gaps were trickier than i originally thought! I did manage to get mine running today although i used an old portable HV DC supply that we had lying around.

Lots of good advice you guys posted - i will dive into all of that tomorrow and respond more! Keep up the good work.

I'm thinking for the final kit to actually use the brass nuts as someone had recommended. Might be a better way of controlling the spark gap distances. And they could be installed using an included shim.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Fri Feb 01 2013, 04:28AM






That is a good idea, the idea behind that to discourage premature sparks as well as reduce corona losses by using a 'curved like' surface as the spark gap electrode. Unfortunately I haven't had much success with the curved spark gaps, and as Alex pointed out, they seem to rely on the encouragement to fire by making the lead sharp and pointed towards each other.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Sat Feb 02 2013, 06:23PM


Any possibility of some photos/short video of yours running? Obviously you wouldn't be able to upload to eastern voltage research's "official" youtube channel, but perhaps you could start a development channel of some sort for small clips like this.

@Houdini0118 and HB how are your marx generators coming along?

BTW I have started work on a switching charging supply for mine, although I am still thinking of a way to add a feedback loop on such a high voltage secondary. Don't want to go off topic here but could anyone point me to some app notes regarding high voltage control loops (SMPS stuff).

A potential devider + optoisolator should work I think, but I am just concerned about efficiency of such a divider.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Sat Feb 02 2013, 06:42PM

i need to work on that i was busy with school stuff but now its the weekend so i will get that working.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Sat Feb 02 2013, 09:39PM

@Alex I have been busy the last few days but plan to mess with it more this weekend sometime. Thinking of doing what you did and try out the marx portion of the kit off a different supply as I haven't solved the mystery of my multiplier not putting out more than i put into it. Glad to see you guys are getting some sparks though!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Sun Feb 03 2013, 04:28AM

yay got it working though it seems not to be firing consistently. It is working nicely off a flyback supply that i think is dc? i removed a huge hv diode from the hv lead but it still seems to work with this so idk. also the spark gaps are very finicy.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Physics Junkie, Sun Feb 03 2013, 05:52AM

Nicely done. It does seem like your spark gaps are trying to form a continuous spark. Adjustment of the gaps will probably solve that

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Feb 11 2013, 12:57PM

Done some modifications to the HV inverter board and the performance of the marx generator is starting to really show its self.

One thing I have defiantly noticed is that with a higher charging voltage the spark gaps are not nearly as sensitive to spacing as they were.

In fact I seem to be experiencing surface tracking too, guess I need to clean the board surface and only pick it up near the ends to avoid finger grease from contaminating it.

Update: Sorry but before I could film it in action a few parts on my modified charger went pop (two diodes and a capacitor). The marx board its self is fine and after replacing the blown parts on the charger that is also working fine, I think I was just asking too much from it.

Those diodes went out with a hell of a bang!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Shrad, Tue Feb 12 2013, 11:17AM

received mine last week, sorry not having mentioned it

neat packaging, nice quality

I'll post a review as soon as I have the opportunity to try them out, I'm currently into some house modifications so this will come later

thanks again for this opportunity!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Wed Feb 13 2013, 03:42PM

Finally got a video of it running with a decent HV supply. Not certain but I think its around 4.4-5kV in, and around 50kV out.

The camera's rolling shutter makes it look like its miss-firing.



Here with a higher charging voltage the 4.7Mohm charging resistor is defiantly needed. It seems spot on for the voltage this marx generator is designed to run on.

The bad news is that I have managed to kill 4 of the resistors toward the end of the board, they have gone open circuit. I remember seeing 2 of the capacitors at the end light up as-well but a quick check on the capacitance meter shows that they have self healed fine with only a small amount of capacitance lost (a few tens of pico-farads).

As it so happened the blown resistors isolated the last two capacitors which retained their charge, I know this as I got a bit of a shock when I went to adjust the gaps. I think I did a little uncontrollable dance at the same time, shame I didn't capture that on film

Here's a note for anyone with this kit, do NOT make your capacitor spark gaps much larger than 4mm! This is what caused my capacitors to momentarily break down and pop a few of the resistors. How ever tempting it is!

@easternvoltageresearch What wattage are the 1Mohm resistors? since they have a ceramic type of body, I am not quite sure what their wattage rating is.

Apologies if my spelling or grammar is off but I have had a bit to drink, and will tidy this post up when I'm sober.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Thu Feb 14 2013, 02:49PM

Thanks for the video. Thats really great. Appreciate you doing that. I will definately upload to our FB page!

The resistors are 1W (although they may be 2W). They are very high quality power resistors, so they were a lot smaller than what you would expect for power vs. size. I will double check.

Thanks again for the video. Nice work!

-Allison

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Sat Mar 09 2013, 05:30PM

This may seem like a basic question, but can't get my head around it.

A lot of diagrams showing the input to a CW multiplier with the 2nd input tied to GND. Does that assume if line voltage is being used, that an isolation transformer is also being used? I would figure that connectin the CW multiplier directly with HOT and NEUTRAL from the line and then measuring the output with respect to EARTH GND and/or discharging to EARTH GND would be the best approach with an unisolated AC input.

What are your thoughts?
Thank you
-A

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Sat Mar 09 2013, 07:53PM

Not sure if this applies here, but any sort of earth to neutral contact in my house results in the RCD tripping.

Would a small isolation transformer be an option (it would only need to be for low current), or would the cost be too much? As that way you could earth one end of the CW.

Think we need someone with more experience to comment though.

Re: Marx Generator Kits - FREE Kits for Evaluation!
doctor electrons, Sun Mar 10 2013, 02:00PM

This may or may not help but this is how most homes in the US are wired.
The ground and neutral in residential homes are the same. They are both tied to the same point in the electrical
panel. The reason is redundancy, if a neutral wire should fail the ground will carry the fault back to the panel and not
through anything else hopefully. Now don't get me wrong here, if you were to wire up a gfci improperly it won't work!
The 240 volt system in most homes has a grounded neutral. Meaning that one leg to neutral will give 120 vac, the other leg to
neutral will also give 120 vac. Leg to leg will give 240. You can also get 120 vac from either leg to ground. (go ahead, meter your
outlets!)
I had a friend that was building some audio gear in his basement. He ran out of outlets at his bench and plugged in an extension
cord run half way across the room. He then found out the hard way that the two outlets he was using were on opposite legs of his
mains. Those little circuits didn't like an unannounced 240v hit!

Re: Marx Generator Kits - FREE Kits for Evaluation!
the mad scientist, Fri Mar 22 2013, 05:40PM

I would absolutely love to have one of these kits.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Thu Nov 07 2013, 02:12PM

UPDATE: Finally respinning the marx generator board with a new arrangement for spark gaps using brass nuts. Stay tuned for more details.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Sun Apr 20 2014, 01:25PM

Good morning everyone. I know its been awhile, but was distracted with other projects.

I have new boards coming in. These will include increasing the size and pulse capacity of the charging resistors, as well as implementing polished brass acorn nuts to be used as spark gaps among other things. I"ll let you know when they come in and those who have previously tested the original marx generator board are welcome to evaluate the play with the new kits.

Stay tuned!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Sun Apr 20 2014, 04:07PM

Awesome! Count me in.

I think increasing the capacity of the charging resistors is a good idea since on the original boards they were very easy to destroy from over voltage if a spark gap is slightly too big.

The capacitors on the other hand seem to be indestructible and self heal after an over voltage event.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Mon Apr 21 2014, 12:36PM

Great! We are also increasing the size of the capacitors ten-fold and increasing the stage count. The total height of the new generator will be about 2-3x longer.

I'll keep you posted!

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Mon Apr 21 2014, 10:35PM


Just saw on facebook that these versions are 100kV. Nice!

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Tue Apr 22 2014, 03:12PM

Theoretically they will be about 100kV. 6kV input with 15 total stages, so in practice the output voltage will probably be around 50-75kV depending on the voltage source and any coronal losses in the system.

But for the intent of the design, that should be plenty voltage as this is intended for educational and desktop use.

The boards have been ordered and should have them by Monday of next week. They are 0.124" FR-4 and measure approx. 2" x 20" in size with vertical mounting provisions. They will also utilize 2W resistors vs. the original wimpy resistors that were used that you guys were blowing and the stage capacitance is also 10x as much.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Tue Apr 22 2014, 11:35PM

Maybe the original resistors were theoretically adequate in power rating, but just physically too small for these voltages? Looking at my evaluation board I can see small streaks down the side of the failed resistors.

Excuse the dust, it lives on a project display shelf in my bedroom.




I guess that a kit like this needs to be run on the conservative side when it comes to component power ratings, which if intended to be sold as an educational kit should be fine. Definitely not in the 4hv spirit of everything is still working lets give it a tad more juice

Wow, how big are those capacitors?

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Wed Apr 23 2014, 01:22AM

The resistors are definitely undersized voltage-wise, but that's just the nature of the beast, especially for something where you want to keep costs down.

True high voltage resistors would probably run about $10-15 each for standard 2W resistors, so you just have to use whats available and inexpensive.

The original Marx generator used 1000pF capacitors. The new one will utilize 10,000pF capacitors.

Again, tough finding high voltage caps economically. Sure, for a one-up build for yourself you could easily scrounge some on Ebay for next to nothing, but for a production release board, you need to find something that will always be readily available and inexpensive as well.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Houdini0118, Wed Apr 23 2014, 02:21AM

Did you get the multiplier for running it off the mains working better as well?

Re: Marx Generator Kits - FREE Kits for Evaluation!
HV Enthusiast, Thu Apr 24 2014, 12:49PM


Great question.
For this and future marx generators, we are actually using a 0-6kVDC high voltage supply board we are designing. It will operate from 15VDC input and provide 0-6kVDC (variable) to charge up the marx generator.

We will still be investigating a better C-W multipler as well as a more cost effective solution to charging up the marx for the amateur with a smaller budget.

Re: Marx Generator Kits - FREE Kits for Evaluation!
HB, Thu Apr 24 2014, 01:33PM

i would also be interested in testing this again if possible.

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Sat Apr 26 2014, 11:00AM


Nice. Which topology are you using?

Re: Marx Generator Kits - FREE Kits for Evaluation!
Alex M, Wed Oct 15 2014, 09:38PM

Update:

So I decided to revisit this project after putting it away when I blew some resistors. I sourced some larger high voltage resistors from CPC (Farnell without the £20 minimum order) and replaced all of the failed resistors on the board.

These resistors appear to be from the same series as the supplied ones but are higher wattage and rated for more voltage, they are YAGEO HHV-50JT-52-1M

This time I left some space between the resistors and PCB to try and discourage surface arcing. On the other side I cut the legs right at the board to help reduce corona loss.



Above: The new resistors compared to the old ones.

This got it working again but I still had problems with the spark gaps being too finicky, jitter and small continuous arcs forming across them. This was down to two things.

• Pointed electrodes that I originally used to encourage sparking.

When I first received the board from EVR I used a measly charging voltage of about 1.5kV from a bug zapper for testing, with such a low voltage the pointed gaps helped to get the process going. But when I switched to a mini flyback/LOPT giving about 5-6kV the leakage at the gaps was enough for continuous arcs to form. This required a large amount of tweaking to get it to fire at a somewhat consistent rate, but even then it sometimes misfired.

• The gaps did not have a direct line of sight with each other

Whilst doing some research on the shapes of spark gaps I came across the following from

The traditional Marx generator operating in air has all the gaps in a line with the electrodes operating horizontally opposed. This allows the UV from bottom gap to irradiate the upper gaps, reducing their jitter. Tests reported in Craggs and Meek showed that obstructing the UV led to greatly increased jitter in the bank output, which they attribute to the lack of UV irradiation on the upper gaps.

With this in mind I set about making some half decent spark gaps that were rounded with a direct line of sight from the first through to the last one for the UV light to travel unobstructed.



The electrodes are just pieces of solid wire with one end bent over in a loop, solder is then generously applied and the surface tension keeps it in there whilst it solidifies.

After doing all of that and tweaking the spacing of the gaps I can now get consistent jitter free sparks at a seemingly faster rate, so fast that I had to add a few more megohm in series with the 4.7Mohm ballast resistor. I guess the corona loading before was large enough to cause significant loss.

I still need to clean the flux residue from the board and some of the electrode legs could do with shortening to reduce parasitic inductance and improve overall neatness.